This study examines zero marking, i.e. the absence of an overt exponent, in adjectival, nominal, and verbal inflectional morphology across languages. The first part of the study provides an overview of the distribution of zero markers in inflection paradigms using the UniMorph dataset. The results show that there is a general preference against zero marking. The distribution of zero markers varies to a great extent across languages and lemmas, the only robust trend being that they are avoided in cells that express a high number of grammatical values. The second part of this study examines the association between marker frequencies and phonological length, using the Universal Dependencies treebanks. While token frequency is a good predictor for the length of overt markers, it does not account for the occurrence of zero markers. This is taken as evidence to support a differential non-development scenario of zero marking rather than a phonetic reduction scenario.